A dealer shall not be entitled to produce additional evidence whether oral or documentary in appeal before the appellate authority or in revision before the Commissioner or the Tribunal except where the evidence sought to be adduced is evidence, which the prescribed authority had wrongly refused to admit or which, after exercise of due diligence, was not within his knowledge or could not be produced by him before the prescribed authority or for the production of which adequate time was not given by the prescribed authority and in every such case upon the additional evidence being taken on record reasonable opportunity for challenge or rebuttal shall be given.